1. Field of the Invention
The present invention relates to a thermally insulating system for packaging perishable goods, particularly perishable food products.
2. Description of the Prior Art
Various types of container systems have been utilized to package perishable goods, such as perishable food products. The packaging of food products for shipment in compartmentalized containers presents several problems, the solutions to which are sometimes in conflict. It is highly desirable for perishable food to be shipped in containers that provide a high degree of cushioning to prevent damage to the food products shipped therewithin. Such damage would otherwise result from impacts to the containers that inevitably occur during loading and unloading, and also during transit on a vehicle. Unfortunately, many of the best cushioning systems are also quite bulky, and therefore, the volume required to accommodate the bulk of these cushioning systems reduces the quantity of perishable goods that can be packed within a limited volume of space.
Another problem of that exists in packaging perishable food products for shipment is that the empty containers that are used to protect the goods during shipment present a storage problem when they are not actually in use. To solve this problem I and others previously devised insulated containers for packaging commercial perishable food products which are fully collapsible so that large numbers of these containers can be stored within a compact volume. These containers and their construction are described in prior U.S. Pat. Nos. 5,820,268; 6,007,467; and 6,080,096.
I have since discovered certain shortcomings in the prior designs. Specifically, all of these prior designs involved the placement of a soft sided, thermally insulating bag within an outer, stiff-walled box. The location of the thermally insulating bag within the confines of the box allows heat to enter the box and surround the bag in the box if the box is left out in the sun or stored within an area of high ambient temperature. This inevitably leads to a rise in temperature within the bag, despite its thermal insulation. Also, the location of the bag within the box reduces the volume of space within the box that can be occupied by food products. As the thickness of the insulating walls of the bag increases, the volume within the box that can be occupied by food products decreases.
Volume within the box is also reduced due to folds created in the soft walls of the thermally insulating bag as the bag conforms to the shape of the enclosure of the box. Such folds do provide dead air spaces which are helpful for installation purposes. However, this advantage is more than offset by the deleterious thermal effect on the contents of the bag by permitting heat to pass through the walls of the box and surround the thermally-insulating bag, and by the significant increase in the volume of space within the box occupied by the bag itself, rather than the contents which the bag is designed to protect.
The present invention provides an extremely useful and simple design for a collapsible container for shipping perishable goods. Stated simply, the concept of my invention involves covering the exterior surfaces of a relatively stiff shipping box with a conforming jacket or skin that is adhesively secured to the exterior surfaces of the box.
A primary advantage of the improved shipping container of the invention is that the thermally insulating skin on the exterior surfaces of the corrugated paperboard structure located therewithin to a large extent prevents heat from entering the enclosure in which the perishable goods are stored and shipped. Unlike conventional systems that allow heat to enter a stiff-walled structure, then attempt to prevent the heat from reaching the perishable goods by providing the corrugated paperboard structure with an inner thermally insulating bag, the present invention, to a large extent, prevents heat from ever entering the enclosure of the corrugated paperboard structure. The surface of the protective skin is preferably coated with a highly reflective coating that reflects most impinging solar radiation and thus precludes heat from ever entering the confines of the protective skin. By providing an insulating barrier on the exterior of the corrugated paperboard structure rather than on the interior, a much more effective thermally insulating barrier is created.
Also, by constructing the shipping container with thermal insulation on the outsides of the stiff walls, rather than on the inside, the volume of space within the stiff walled box is increased while still maintaining the advantages of thermal insulation provided by my prior systems.
A further advantage of adhesively securing a skin or jacket to the exterior surfaces of a relatively stiff shipping box is that it is easier to make the thermally insulating material conform to the shape of the exterior wall of a box, rather than the interior. As a consequence, shipping containers of this type can be closely packed together both for use in an uncollapsed and expanded form when utilized for the shipment of perishable goods. These shipping containers also occupy less space when collapsed for storage during periods of nonuse.
In one broad aspect the present the invention may be considered to be a collapsible shipping container for perishable goods comprising an inner stiff-walled structure formed of corrugated paperboard and an outer skin comprised of thermally insulating material adhesively secured to the inner walled structure. The thermally insulating material may take several forms. For example, the thermally insulating material may be comprised of a plastic bubble packing layer faced on both sides with. plastic film layers. The inner plastic film layer is adhesively secured to the outer surfaces of the inner stiff-walled structure. The other plastic film layer is preferably an exterior layer having a light-reflective coating thereon. The coating is preferably an aluminum color that reflects visible light and infrared radiation as well. In the preferred embodiments the plastic forming the thermally insulating material is polyethylene.
Alternatively, the thermally insulating material may be comprised of a plastic foam layer faced on one side with a plastic film layer. The film layer may have a light-reflective coating while the foam layer may be formed of polyethylene or polyurethane. In still another embodiment the thermally insulating material may be comprised solely of a sheet of light-reflective polyethylene.
In any event, in the thermally insulating material forming the outer skin completely covers the exterior surfaces of the inner, stiff-walled corrugated paperboard structure. While in a flattened condition the exterior surfaces of the corrugated paperboard structure are sprayed with an adhesive and then the outer thermally insulating skin is laid upon the adhesively coated corrugated paperboard structure so that the skin and the paperboard are adhesively secured together throughout their surfaces of mutual contact.
In another broad aspect the invention may be considered to be a shipping container for perishable goods comprising: a stiff walled inner liner forming an enclosure of defined shape and fabricated from corrugated paperboard with outwardly facing surfaces and an overlying jacket formed of thermally insulating material and having an inwardly facing surface that resides in contact with and is adhesively secured to the outwardly facing surfaces of the inner liner.
In still another aspect the invention may be considered to be a collapsible shipping container for perishable goods comprising: an inner, stiff, corrugated paperboard box having interior surfaces forming an enclosure of defined shape and opposing exterior surfaces, and a surrounding skin of thermally insulating material adhesively secured to the exterior surfaces to envelop the box therewithin.
The invention may be described with greater clarity and particularity by reference to the accompanying drawings.